Sub-700fs pulses at 152 W average power from a Tm-doped fiber CPA system

Thulium-based fiber lasers potentially provide for the demand of high average-power ultrafast laser systems operating at an emission wavelength around 2 mu m. In this work we use a Tm-doped photonic-crystal fiber (PCF) with a mode field diameter of 36 mu m enabling high peak powers without the onset of detrimental nonlinear effects. For the first time a Tmdoped PCF amplifier allows for a pump-power limited average output power of 241 W with a slope efficiency above 50%, good beam quality and linear polarization. A record compressed average power of 152 W and a pulse peak power of more than 4 MW at sub-700 fs pulse duration are enabled by dielectric gratings with diffraction efficiencies higher than 98% leading to a total compression efficiency of more than 70%. A further increase of pulse peak power towards the GW-level is planned by employing Tm-doped large-pitch fibers with mode field diameters well above 50 mu m. The coherent combination of ultrafast pulses might eventually lead to kW-level average power and multi-GW peak power.